Plastic barrier materials are involved in an almost unlimited range of products and applications. Containers, wrappers, pouches and bottles of varying degrees of flexibility for foods, pharmaceuticals, chemicals, and myriad other products are commonplace. In addition to containing and protecting products, barrier sheet materials are used to protect equipment and even personnel from a wide range of environmental hazards. One application of such barriers having particularly stringent demands is that of protecting military personnel, equipment, and supplies. Here, in additions to being fire-retardant, the material should protect against a wide range of chemical and biological agents. It should also resist penetration liquids, gases, dust, including radioactive dust and not be susceptible to deterioration from ultraviolet light. Of course, the material should also be durable and relatively easily repaired when torn or punctured. In some instances where the barrier material is to be used in tents, equipment enclosures, or covers, it should have an outer surface in a mat finish and dull color to escape detection from the air. The outer surface should also be "printable" in that it should easily accept printed patterns such as those needed for camouflage.
Because the attainment of some of these qualities often results in the sacrifice of others, e.g. the addition of a fire retardant material to a material may affect its durability, there is not presently available a material which even nearly satisfies the needs of the military.
One of the better known commercial films sometimes used as a barrier is the copolymer of vinylidene chloride and vinyl chloride sold by the Dow Chemical company under the trademark SARAN.RTM.. It has a high resistance to attack by a wide range of chemicals, it has low permeability to gases and vapors, and it has high transparency. Moreover, it can be bonded or sealed to itself and to many other materials and substrates for special applications. The Dow company has made and sold widely combinations of SARAN.RTM. and outer layers of polyolefin resins including low density polyethylene (LDPE) and ethylene vinyl acetate (EVA) under the trademark SARANEX.RTM.. The SARANEX.RTM. films in turn have been further laminated or bonded to yet other materials. In an attempt to fill the need for a fire-retardant barrier film, it is believed that among the materials Dow has included with or added to SARANEX.RTM. is chlorinated polyethylene. However, it is believed that such combinations were not successful in meeting the requirements of a practical fire-retardant barrier.